Rear Geared Hub Motors - Advice

[Roncos]

I'm researching a diy ebike project. Planning to use rear geared hub motor and pedal assist setup with teensy 3.2 as microcontroller. Today I'm looking at hub motor selection.

Does anyone have experience of the motor at the link below? Would anyone recommend this or an other?

Is it suitable for use with rim brakes? Can the wheel rim be readily centered in the frame?
Is the motor fitted with hall sensors or is it for s sensorless controller?
Lastly how difficult is it to lace up the wheel? Is this a day or two of reading/learning/trial and error or is it a dark art that requires an apprenticeship?

http://www.ebay.co.uk/itm/48V-500W-8Fun-Bafang-Brushless-Geared-Cassette-Hub-Motor-For-Rear-Wheel-/232088812478?hash=item3609923bbe:g:jzgAAOSweWVXdN4c

Thanks

R

 

[Ykick]

Looks like a Bafang BMP2 or close to that? I have no experience with those. It does mention Hall Sensor optional so I would assume it will work sensored which is the only way I run these smaller geared hub motors. I've worked with Q100/128 geared hubs.

Here's one place that sells them - https://bmsbattery.com/38-rear-driving?p=2

Lacing is relatively easy for hub motor wheels because it usually requires only 1 cross pattern.

Truing is more of the “art” about wheel building. But the good news is that you can start learning and practicing spoked wheel truing today.

Get a spoke wrench, maybe some wire ties (use the later for a crude runout gauge) and get to work on whatever bicycle wheels you currently have at your disposal.

Practice makes perfect but if you have some mechanical aptitude, you’ll quickly develop an understanding how spoke tensioning can pull and move rims around a hub.

Good luck and do some searches for Bafang BMP2…

 

[motomech]

As usual, lot's of confusing info about motor speed, the single most important critiera when selecting a hub motor.
(Here is a good explanation of the relationship of motor speed, desired road speed and how it effects controller selection;
http://em3ev.com/store/index.php?route=product/product&path=50_40&product_id=52
I have never seen the rating values used on that Ebay site and even the BMS Battery ratings are somewhat obtuse.
Commonly, the motor speed is rated as "No-load speed @ 36V" and while the actual number may vary, virtualy all hub motors are rated this way and that makes the rating relevant by way of comparison to other motors.
One will note, the 36 V BPM CST @ the BMS B. site is also rated w/ the ambiguous "Maximum speed(RPM): 270", same as the 48 V version. Now we know the 36 V CST, which has been around a while, is in fact, a 270 rpm motor at 36 V, making it a mid-speed motor. Now, does that mean the 48 V version is rated at 48 Volts, which would mean that at 36 V, it would be 201 rpm, which is a low speed motor?
Another Chinese mystery
You might contact BMS B. and ask them what the 48 V CST motor speed is @ 36 Volts and see what they say?
Here is the Grin motor sim., which lists the 36 V BPM CST as an option;
http://www.ebikes.ca/tools/simulator.html

 

[Roncos]

Thanks for the info guys. One more question, do you know the UK customs duty for these motors?

 

[d8veh]

That motor is a Bafang CST. They're very reliable and give good torque. You can run them reliably up to 30 amps (36v) and 25 amps (48v). The key thing about that motor is that it has the cassette spline, so you can have a nice gear setup or keep your existing gears when you have a decent bike. £135 is a good price for one of those. I used to pay £250.

With a hub-motor, the RPM is important. That one (500w) does 315 rpm at 48v, which is about 23 mph with a 26" wheel. At 36v, it's only 240 rpm, which is 18 mph max. Both will give about 10% more speed with a fully charged battery, but the speed will reduce as the battery goes down.

The motor doesn't care whether you have rim brakes or disc. It's only the rim that decides that. A rim brake rim can be used with either. The motor has the fixing points for a disc so you can use either, but I'd recommend a hydraulic disc brake because rim brakes are barely adequate for electric bikes.

Lacing a rim is not too difficult. It's a good skill to learn. You choose your rim, then you have to calculate the spoke length with an on-line spoke calculator. It's best to have the rim in your possession before you do that because you can't rely on the ERD given in listings. If you need any help with that, post again after you have the motor and rim.